DC, Marvel and such.
I used to read these a lot when I were a lad, but could never remember at what sort of age. It was obviously after I grew out of reading the Dandy, Beano and such, and before I started reading the NME (it would have been either/or, rather than as well as, given the limited amount of pocket money I had). Anyway, I was idly searching on the internet for clues, and I came across a description of a story-line I recognised. The magazine in question was published in 1961, which seems a bit early (I would only have been seven), but the comics might have taken a while to filter through to the UK, so maybe I was eight.
One thing I remember was that they had an advert in the back urging their young readers to 'Sell Grit!', which always baffled me. There used to be offers for ludicrous numbers of toy soldiers for some pathetically small amount of money which tempted me, but you had to pay by International Money Order, and i had no idea what one of those was, or how to get hold of one.